Is my mesh too complex?
Yes, your model is probably too detailed for a game scene background. Moreover, since it's a rather simplex geometry, the face count may be easily reduced with no noticeable effect on its appearance. As it was pointed out, you currently have almost 25,000 faces, that are unnecessarily too many for the surface of your toilet.

(Note: high-poly and low-poly mean high or low polygon count, polygons being your mesh's faces)

"Decimate" the number of faces



From the Properties window, Modifiers panel, click "Add modifier" and select "Decimate". Your face count is displayed as "Faces: Xxxx" on the bottom of the "Decimate" box.

The three methods (Collapse, Un-Subdivide and Planar) are described here: https://docs.blender.org/manual/en/dev/modeling/modifiers/generate/decimate.html

To see any effect, you must:


on "Collapse", reduce the ratio (try something around 0.33: it'll reduce the face count by two thirds)
on "Un-Subdivide", increase the number of iterations to 1 or 2
on "Planar", change the threshold angle to 3-4 degrees.


(choose one of the three, whichever looks the best)

When you change these values, you can see the updated number of faces updated under your slider. Also, your model gets updated live in the 3D-view. Choose the lowest number of faces that still keeps the appearance good and smooth enough. 

Once you are done, hit "Apply" in the decimate box.